QSFP+ Interconnect Solution for 40 Gigabit Ethernet

The QSFP+ optical transceiver is the dominant transceiver form factor used for 40 Gigabit Ethernet applications. In the year of 2010, the IEEE standard 802.3ba released several 40-Gbps based solutions, including a 40GBASE-SR4 parallel optics solution for multimode fiber. Since then, several other 40G interfaces have been released, including 40GBASE-CSR4, which is similar to 40GBASE-SR4 but extends the distance capabilities.

As is know to all, two switches are connected by either transceiver modules or cables. For example, if you simply wanted to cable up two Nexus 3000s with 40GbE, the options are multi mode fiber or twinax copper. We’ll only cover the fiber throughout this post as that is where most of the questions are in recent years. So, since you are now using fiber, how do we connect these switches into the network? First, you need to insert the QSFP+ optic similar to how you would insert a fiber optic for standard 1G or 10G connectivity. For the Nexus 3000, only multi mode fiber is available, so the Cisco part number needed is QSFP-40G-CSR4. This is the equivalent of the GLC-LH-SMD or SFP-10G-SR, for 1G and 10G, respectively. The connector type for QSFP-40G-CSR4 is no longer LC, but is a MPO (multi-fiber push-on) connector.

It is worth noticing that cables for 40G Ethernet actually have 12 fiber strands internal to them to achieve 40GbE. Distance limitations are 100m using OM3 and 150m using OM4 fiber respectively. Because these cables are connected with MPO connectors, have 12 strands, and are ribbon cables for native 40GbE. They will not be able to leverage any of your existing fiber optic cable plant. So be prepared to home run these cable where needed throughout the data center.

However, you may not always need native 40GbE between two switches. Instead, you may opt to configure multiple 10GbE interfaces instead. In this case, the QSFP-40G-SR4 is still needed, but the cable selection is different with what was previously shown above and the ability to use current cable plants is possible. The cable required here would have an MPO connector on one end that would connect into the QSFP port and then “break out” into 4 individual fiber links on the other end. These breakout cables terminate with LC male connectors. I would like to call it MTP-LC harness cable. The application for this MTP-LC harness cable is to directly connect a QSFP+ port to (4) SFP+ ports. For most Data Center applications, the use of structured cabling is employed via MTP trunks and the use of patch panels.

This is great that they terminate with LC male connectors because this allows customers to leverage the current cable infrastructure assuming existing patch panels have LC interfaces and OM3/OM4 fiber is used throughout the data center. These breakout cables are also nice if you want to attach a northbound switch that only supports 10GbE interfaces. You can easily direct connect or jump through a panel in the data center to connect the Nexus 3000 via multiple 10GbE interfaces to a Nexus 7000 (or any other switch with 10GbE-only interfaces).

Accordingly, direct attach cables which are terminated with QSFP+ connector is an alternative in 40G connectivity. For instance, HP JG331A compatible QSFP+ to 4SFP+ direct attach copper cable is terminated with one QSFP+ connector on one end and four SFP+ connector on the other end.

40G QSFP+ cables can provide inexpensive and reliable 40G speed connections using either copper cables with distances reaching up to 30ft (10 meters length) or active optical cables reaching even 300ft (100 meters). Cost of local NOC connectivity is significantly reduced by avoiding the more costly fiber transceivers and optical cables.

Guide to High-Speed Copper Transceivers

The last few decades have seen the broad adoption of fiber optic transceivers used in optical communications for both telecommunication and data communications applications. However, would the copper connectivity withdraw from the market? Copper medium usually doesn’t require any transceivers, as they are part of the interface module. However, in order to cut down expenditures, some vendors use SFP copper transceiver with an RJ-45 female connector for Gigabit Ethernet connectivity over copper medium, or XFP copper transceiver for 10Gigabit Ethernet (10GbE) connectivity over CX4 copper. This article will give you a complete guide to these copper transceivers.

Supporting 10/100/1000 Mbps data-rate in excess of 100 meters (325 feet) reach over UTP Category5/5e cables, copper transceiver module is ideally suited for implementing small form-factor Network Interface Cards (NICs) and uplinks. As such, it is highly appropriate for use in high-density applications such as LAN 1000BASE-T, switch-to-switch interfaces, switched backplanes, blade servers, gaming devices, and router/server interfaces.

With the development of 1000BASE-T technology, 1000BASE-T and 100BASE-TX copper SFP transceiver over Category 5 copper cabling is an attractive option for network. The advantages are listed as follows:

• For 100m reach over Cat 5 UTP cable
• Hot-pluggable SFP footprint
• Supports RX_LOS as link indication function
• Fully metallic enclosure for low EMI
• Low power dissipation (1.05 W typical)
• Compact RJ-45 connector assembly
• Compliant with SFP MSA and IEEE Std 802.3-2002

Here are two good examples of 1000BASE-T copper SFP transceivers, the Finisar FCLF-8521-3 compatible 1000BASE-T SFP copper transceiver and HP J8177C compatible 1000BASE-T SFP copper transceiver from FS.COM. Both of them are designed for 100m reach over Cat 5 UTP cable with RJ-45 interface and support max data rate of 1000Mbps.

As a kind of copper XFP transceiver, the XFP 10GBASE-CX4 module uses a CX4 connector to provide a connection to up to 15 meters over CX4 grade copper cable. Transparently to the user, the module transfers the 10GbE data stream over four full-duplex 3.125 Gbps channels over a single parallel copper cable. The product offers the ability to scale bandwidth in 10G increments, and directly with the industry standard MDI electrical socket.

CX4 is an extension of the four-channel 10 Gbps XAUI interface and is available in 70-pin MSA transponder modules, otherwise known as Xenpak, XPAK and X2. The 10GBASE-CX4 solution employs an Infiniband-style Twin-AX cable (click to see the Cisco 10G twinax). In this case, eight 100-ohm differential Twin-AX cables are bundled into a single outer shield. The center conductors are 24 AWG wire for compatibility with printed circuit board termination inside the connector housing. The limitation of the 10GBASE-CX4 solution is that it requires a 70-pin MSA socket and only supports the IEEE802.3ae 10GE data format.

The XFP format also offers the distinct feature of being data agnostic, which opens the market for the copper based solution to telecommunications applications as well. The 10 Gbps serial solution over copper adds the final link option to the XFP industry, offering everything from the ultra low-cost sub-20m 10 Gbps shelf-to-shelf and rack-to-rack links to 80 km or longer optical links.

Among the above-mentioned copper transceivers, what must be noticed is that copper SFP transceiver offers a flexible and simple method to be installed into SFP MSA compliant ports at any time with no interruption of the host equipment operation. It enables for seamless integration of fiber with copper LAN connections wherever SFP interface slots can be found. Such system is economical, it saves time, offers flexibility and eliminates the necessity for replacing entire devices once the customers have to change or upgrade fiber connections and you will benefit so much from it.

3 Ways Third-Party Transceivers Benefit Your Data Center

Are you still spending hundreds of dollars on the expensive optical transceiver modules for your network system in the data center? In order to cut down the costs on the expensive transceiver modules, many companies are seeking for a compatible third-party transceiver to use. For example, if your network contains Juniper routers, firewalls, and switches, you might think that only Juniper SFP branded transceivers will ensure that all of your equipment is compatible and functions optimally. However, that seemingly reasonable assumption could cost your company thousands of dollars. Compared to the third-party optical transceiver produced by third-party companies, Juniper SFP transceiver comes with dramatically inflated price tags while a third-party compatible one is roughly 80 percent less expensive than Juniper branded SFP transceiver.

What Does "Third-Party" Mean?

In commerce, a "third-party" means a supplier (or service provider) who is not directly controlled by either the seller (first party) or the customer/buyer (second party) in a business transaction. For example, in the fiber optics industry, all fiber optic transceivers are defined by Multi-Source Agreement (MSA). MSAs strictly define the operating characteristics of fiber optic networking equipment, so that system vendors may implement ports in their devices that allow MSA compliant networking components produced by different manufacturers are interoperable. As long as a manufacturer complies to MSA guidelines, their transceiver modules will function and operate identically to any other manufacturer's MSA-compliant transceivers. For instance, HP BladeSystem 455883-B21 compatible 10GBASE-SR SFP+ transceiver from FS.COM will function identically to a HP 455883-B21 transceiver and will be 100% compatible with HP networking equipment.  

Optical transceivers are some of the most all-around useful pieces of hardware for a network. As long as your equipment has SFP/SFP+ ports -which most do- transceivers allow you to change between a multitude of uplink types, to fit whatever wiring you have or will have in the future. They're simple, plug-and-play, and hot-swappable. Third-party optical transceivers can easily prevent thousands of dollars in new hardware costs. In spite of what's often implied by official documentation, a quality third-party optical transceiver is 100% compatible with name-brand equipment. There's simply no difference between good quality third-party transceivers and branded ones. So why choose to pay more?

Three Reasons Why Third-Party Optical Transceivers Just Make Sense

1. Low costs
The lower costs of third-party optics really cannot be overstated. Depending on the model, name brands are anywhere from 50% to 1000% more expensive than third-party alternatives. For example, you can get the Cisco QSFP-40G-CSR4 compatible 40GBASE-CSR4 QSFP+ transceiver with only $110 at FS.COM which ensures the same performance with a Cisco branded QSFP-40G-CSR4 transceiver.  

In many cases, a full loadout of third-party transceivers can shave so much money off of an upgrade budget to fund entirely new pieces of hardware. Or they can put a piece of equipment within range, which wouldn't have been if name-brand ports had to be purchased.

2. Full standards compliance
Only a few factories in the world produce optics, and they make the transceivers for everyone. Those heavily-discounted third-party may be made in the same facilities as the official Cisco, HP, or Juniper units. And since transceivers are fully specified by internationally agreed-upon standards anyway, there's no risk of incompatibilities.

All it takes is code loaded on an EPROM -included in the transceiver- identifying it to your networking hardware and, basically, your equipment can't tell the difference.

3. Lifetime warranty
Besides having much higher prices, the name-brand transceivers also tend to have fairly short warranty periods. It's generally anywhere from a couple years, down to only 90 days. While failure is fairly rare, it's unfortunate that they have such short warranty periods, especially compared to the hardware they're used in.

However, when you buy third-party optics from FS.COM, you will get a full lifetime warranty. That's how certain we are that they truly are of quality equal or better to the name-brand units. As long as your transceivers are in use, they're covered under warranty.

Conclusion

If you're still hesitant about trying a compatible SFP transceiver from a third party manufacturer, the best way to ensure that you're getting a reliable product at a good deal is to choose a vendor you trust, one with a proven track record of quality products and great customer service. Really, there's no compelling reason to over-pay for the name brand optics. Just like buying generic medications at the pharmacy, there is truly no difference aside from the name that's on the packaging.

Optical Loss Testing - Why It Is Important

The Concept of Optical Loss Testing

Optical loss testing is very necessary to evaluate the performance of fiber optic components, cable plants and systems. As the components like fiber, connectors, splices, LED or laser sources, detectors and receivers are being developed, testing confirms their performance specifications and helps understand how they will work together. Designers of fiber optic cable plants and networks depend on these specifications to determine if networks will work for the planned applications.

Providing an accurate method for optical loss testing of multimode fiber is becoming a lot more important for higher data rate applications that place more stringent requirements on the maximum allowable loss for a channel between an optical transmitter and an optical receiver. The higher the data rate, the tighter the loss budget for a channel. The maximum allowable loss for a 10Gb/s Ethernet channel over OM3 multimode fiber is 2.6 dB. The maximum allowable loss for a 40 Gb/s and a 100 Gb/s Ethernet channel is 1.9 dB over OM3 fiber and 1.5 dB over OM4 fiber.

Ethernet	OM3 IL max.(dB)	OM4 IL max.(dB)
1000BASE-SX	4.5	4.8*
10GBASE-SR	2.6	3.1*
40GBASE-SR4	1.9	1.5
100GBASE-SR10	1.9	1.5

Factors That Affect The Accuracy of Optical Loss Testing

Optical loss testing of multimode fiber can be affected by many factors, among which there are several major factors that can affect the testing accuracy for optical loss measurements. These include:

1.The type and quality of the “test reference cords”
The type and quality of the “test reference cord” is critical for accurate optical loss measurements in the field. The end-face geometry of the polished ferrule on the cord connector can have a significant effect on the test results and must meet precise parameters such as radius of curvature, apex and fiber protrusion.

2.Fiber mismatch between the test reference cords and the link under test
Fiber mismatches are the result of inherent fiber characteristics and are independent of the techniques used to join the two optical fibers. The intrinsic coupling loss due to fiber mismatch include core diameter differences, core/cladding concentricity error, numerical aperture differences.

3.The characteristics of light source and how light is coupled into the fiber
The launch conditions and how light is coupled into the fiber can have the greatest effect on optical loss measurements. For multimode fiber, different distributions of launch power (launch conditions) can result in different attenuation measurements.

Testing Tools

Various types of testing equipment are available on the market, such as a fiber visual fault locator (VFL), a fiber power meter, a network cable tester or an optical time-domain reflectometer (OTDR).

Fiber optic cable testing needs special tools and instruments. And they must be appropriate for the components or cable plants being tested. The following five kinds of fiber testing tools are needed for the testing work.

• OLTS—Optical loss test set (OLTS) with optical ratings matching the specifications of the installed system (fiber type and transmitter wavelength and type) and proper connector adapters. Power meter and source are also needed for testing transmitter and receiver power for the system testing.
• Reference test cable—This cable should be with proper sized fiber and connectors and compatible mating adapters of known good quality. And the connector loss is less than 0.5 dB.
• VFL—Visual fiber tracer or visual fault locator (VFL)
• Microscope—Connector inspection microscope with magnification of 100-200X, video microscopes recommended.
• Cleaning Materials—Cleaning materials intended specifically for the cleaning of fiber optic connectors, such as dry cleaning kits or lint free cleaning wipes and pure alcohol.

Conclusion

Optical loss testing is not as simple as it seems and can be affected by many variables, including fiber mismatch, the type and quality of the test reference cords and the launch conditions (OFL/Mandrel wrap versus Encircled Flux). The more stringent optical loss requirements for high speed applications necessitate an accurate test method for testing links in the field. FS.COM offers a wide selection of fiber testers & tools to fit any fiber optic cable lineman or powerline worker jobs. We stock top high quality test equipment for the communications applications. In the fiber optic installation and maintenance works, Optical Power Meters, Fiber Light Sources, Fiber Scopes and OTDR are commonly used for fiber optic testing. And Splicing fiber tools, termination tool kits and cleaning tools, like strippers, cable cutters, splice protective sleeves help work easier. Besides, high quality fiber cables, such as MPO cable, Push-Pull LC cable and so on are also available for your choice.

Reference: http://kellyzeng.inube.com/blog/4748262/optical-fiber-loss-testing/

24-fiber MPO/MTP Solution for 40/100G Migration

Since IEEE 802.3ba 40GBASE-SR4 and 100GBASE-SR10 were ratified in 2010, 24-fiber connectivity has been adopted as the ideal migration solution in the data center. Using 24-fiber cabling throughout an entire channel provides extra flexibility, as users can easily migrate from 10G to 40G or 100G by simply swapping out the connectivity at the end of the channel. Pre-terminated cabling using 24-fiber connectors provides double the density of 12-fiber cabling in the same footprint, reducing the cabling required, allowing for fewer cable pathways, and improving airflow in data centers. Next we will take a closer look at the advantages of 24-fiber MPO/MTP solution in 10G to 40/100G migration.

In choosing the migration path from 10G to 40/100 G, there are generally two options: the 12-fiber MPO/MTP solution or 24-fiber MPO/MTP solution. A 12-fiber MPO/MTP connector is used for 40 GbE (data rate up to 40Gbps, 4 x 10 Gbps). But among the 12 fibers, only 8 optical fibers are required—4 for Tx and 4 for Rx, and each channel has a transmission rate of 10 Gbps (usually use the 4 left and 4 right optical fibers, and the inner 4 optical fibers are left unused). And for 100 GbE (data rate up to 100 Gbps, 10 x 10 Gbps or 4 x 25 Gbps), there are two solutions. One is to use two 12-fiber MPO/MTP connectors, one transmitting 10 Gbps on 10 fibers and the other receiving 10 Gbps on 10 fibers. The other is to use a 24-fiber MPO/MTP connector. Among the 24 fibers, only 20 fibers in the middle of the connector are used to transmit and receive at 10 Gbps and the 2 top and bottom fibers on the left and right are unused. Why the 24-fiber is superior to 24-fiber? We’ll see the advantages from the following aspects.

Maximum Fiber Utilization

Using 24-fiber trunk cables with 24-fiber MPO/MTP connectors on both ends to connect from the back of the switch panel to the equipment distribution area can maximum the fiber utilization. For 10G applications, each of the 24 fibers can be used to transmit 10 Gbps, for a total of 12 links. For 40G applications, which requires 8 fibers (4 Tx and 4 Rx), a 24-fiber trunk cable provides a total of three 40G links. For 100 GbE, which requires 20 fibers (10 Tx and 10 Rx), a 24-fiber trunk cable provides a single 100G link (24-fiber solution is the more recommended configuration to used for 100 GbE than 12-fiber solution). This recoups 33% of the fibers that would be lost with 12-fiber trunk cables, providing a much better return on investment.

Reduced Cable Congestion

24-fiber trunk cables provide more amount of fiber in less space. For instance, it takes three 12-fiber trunk cables to provide the same number of links as a single 24-fiber trunk cable—or about 1-1/2 times more pathway space for a 40G application.

Increase Fiber Density

Density in fiber switch panels is critical as today’s large core switches occupying upwards of 1/3 of an entire rack. 24-fiber MPO connectors offer a small footprint which can ultimately provide increased density in fiber panels at the switch location. In addition, with fanout technology, a 24-fiber MPO cable can be designed with a 24-fiber MPO on one end and 12 duplex LCs on the other end which is an ideal solution for high density 40/100 GbE migration.  

Simple and Cost-effective

24-fiber MPO/MTP solution is a simple and cost effective migration path from 10G to 40/100G Ethernet. It effectively supports all three applications—10, 40 and 100 GbE. Data center managers can easily migrate to higher speeds, with less time and complexity, as 24-fiber solution offers guaranteed performance for 10, 40 and 100G applications, upgrading the cabling infrastructure is as simple as upgrading the fan-out cables or cassettes and fiber patch cords to the equipment.

24-fiber MPO/MTP solution provides an efficient way to migrate your network from 10 to 40 and 100 GbE. Choosing the right migration path not only helps you reach maximum benefit but also cut down the expenditures. Of course, choosing a good vendor is also a must. Fiberstore (FS.COM) may be your good choice. For more information, please contact us via sales@fs.com.

Connectivity Options for 10 Gigabit Ethernet

Since March 1999, the Ethernet industry has been working on providing solutions to increase the speed of Ethernet from 1 to 10 gigabits per second. For enterprise LAN applications, 10 Gigabit Ethernet enables network managers to scale their Ethernet networks from 10 Mbps to 10,000 Mbps, while leveraging their investments in Ethernet as they increase their network performance. There are various types of cables and transceivers available for making Ethernet connections at speeds of 10 Gigabit per second. This article will illustrate both the copper and fiber connectivity options for 10 Gigabit Ethernet.

Transceivers

Standards bodies initially offered several options for the 10-Gigabit transceiver. The one that ultimately evolved as most popular in commercial data center usage was the XFP transceiver. In recent years an extension of the SFP transceiver was standardized for use with 10 Gigabit Ethernet and named SFP+. SFP+ has three outstanding advantages. First of all, it was smaller than the XFP form factor allowing for much more dense packaging of ports on (primarily) switches. Secondly, a new type of very short distance copper cable was developed which uses the same mechanical form factor as the optical transceiver and is capable of carrying 10Gbps Ethernet data. This cable type is called direct attach copper cable which will be introduced later. SFP+ has now become the predominant 10G Ethernet connector type.

Fiber Cables

Fiber cables consist of the cable itself and the connectors on the ends. There are multiple choices for cable type and for connector type. The difference in cable choices come from the distance limitations encountered with the various types of optical transmission. The commonly available types of fiber cables include: SR for connections of up to 300 m in length, LR for connections of up to 2 km in length and ER for connections of up to 10 km in length.

Copper Cables

• 10GBASE-T
  For 10-Gigabit Ethernet cabling, the standards body determined that even enhanced Cat5e UTP traditional Ethernet cable would not be able to carry the signal reliably for any significant distance. So a new specification which still uses RJ45 connectors was introduced and is commonly referred to by its standards name 10GBASE-T. It calls for a 4-wire twisted pair cable with even more strinent limitations on cross-talk.
• CX4
  CX4 is a cable type generally associated with an alternative networking technology called InfiniBand. CX4 cable can also be used in 10Gigabit Ethernet connections. It uses a coaxial copper cable and can support cable lengths of up to 15m.
• SFP+
  As discussed above, one of the advantages of the SFP+ connector type was that a new type of very-short-distance copper cable was developed which uses the same mechanical form factor as the optical transceiver and is capable of carrying 10Gbps Ethernet data. This cable type namely SFP+ direct attach copper cable is a fixed assembly that is purchased at a given length, with the SFP+ connector modules permanently attached to each end of the cable. It provides high performance in 10 Gigabit Ethernet network applications, using an enhanced SFP+ connector to send 10 Gbps data through one paired transmitters and receivers over a thin twinax cable.

To conclude, 10 Gigabit Ethernet has become the technology of choice for enterprise, metropolitan, and wide area networks. Choosing the right kind of connectivity options helps you ensure the proper and efficient performance of your networks. Fiberstore offers various kinds of fiber optical transceivers for 10 Gigabit Ethernet, such as the HP J9151A, NETGEAR AXM761 SFP+ transceiver and so on. Besides, cables for 10 Gigabit Ethernet can be customized according to your special requirements. 

QSFP+ Optics for High-Density 40GE Connectivity

With the development of the SFF-8436 Multi Source Agreement, many vendor are now offering a variety of IEEE- and MSA-compliant Quad Small Form-Factor Pluggable Plus (QSFP+) devices for fiber networks. And there are basic three 40G QSFP+ optics for this standard: 40G LR4 QSFP+ transceiver, 40G SR4 QSFP+ transceiver and 40G LR4 parallel single mode (PSM) transceiver. This article will take a close look at these 40G QSFP+ optics for high-density 40 GE connectivity.

40G LR4 QSFP+ Transceiver

Conforming to the 802.3ba (40GBASE-LR4) standard, the 40G LR4 QSFP+ transceiver together with the LC connector can support an optical link length up to 10 kilometers over single mode fiber. For example, the following Juniper JNP-QSFP-40G-LR4 compatible 40GBASE-LR4 QSFP+ transceiver offers 4 independent transmit and receive channels, supporting link distance of 10 km over single mode fiber. In the process of transmitting, this kind of transceiver has to introduce MUX/DEMUX to multiplex/de-multiplex optical signals.

The working principle of this kind of QSFP+ transceiver is : in the transmit side, four 10 Gbp/s serial data streams are passed to laser drivers. The laser drivers control directly modulated lasers (DMLs) with wavelengths. the output of the four DMLs are optically multiplexed to a single-mode fiber through an industry-standard LC connector. In the receive side, the four 10 Gbp/s optical data streams are optically de-multiplexed by the integrated optical demultiplexer; then, each data steam is recovered by a PIN photodetector/transimpedance amplifier and passed to an output driver.

40G SR4 QSFP+ Transceiver

The 40G SR4 QSFP+ transceiver, conforming to the 802.3ba (40GBASE-SR4) standard, provides a 40G optical connection using MPO/MTP fiber ribbon connectors. Unlike the 40G LR4 QSFP+ transceiver, this kind of transceiver are used together with multi-mode fiber, supporting with a link length up to 100 meters on OM3 cable and 150 meters on OM4 cable.

The operating principle of the 40G SR4 QSFP+ Transceiver is : the transmitter convertsparallel electrical input signals into parallel optical signals through the use of a laser array. Then the parallel optical signals are transmitted parallelly through the multi-mode fiber ribbon. Reversely, the receiver converts parallel optical input signals via a photo detector array into parallel electrical output signals.

40G LR4 Parallel Single Mode (PSM) Transceiver

40G PSM transceivers are used to provide support for up to four 10Gb Ethernet connections on a QSFP+ port over single mode fiber. These transceivers support distance of up to 10 kilometers over single mode fiber using an 8 parallel fiber MPO interface. Each fiber pair can be broken out to a 10Gb Ethernet connection, compatible with up to four 10GBASE-LR interfaces. The MPO to 4 x LC single mode fiber patch cord can be used to breakout the 4 fiber pair of the MPO parallel connector to 4 separate fiber pairs.

Summary

To sum up, 40G SR4 QSFP+ transceivers are suitable for short-distance transmissions. So they are often used in data centers to interconnect two Ethernet switches with 12 lane ribbon OM3/OM4 cables. while 40G LR4 QSFP+ transceivers and 40G LR4 PSM transceivers are often used in long-distance transmission applications. Fiberstore offers a wide range of 40G QSFP+ transceivers, like 40GBASE-SR4, 40GBASE-LR4, 40GBASE-CR4 QSFP+ transceivers, etc. Besides, we also provide 40G direct attach cables, such as Juniper QFX-QSFP-DAC-1M, Cisco QSFP-4X10G-AOC3M and so on.

Reference:http://www.fiber-optic-transceiver-module.com/basic-40g-qsfp-optics-for-40g-transmission.html